1. Field of the Invention
The present invention pertains to medical equipment, and more particularly, to a therapeutic ultrasound system for ablating obstructions within tubular anatomical structures such as blood vessels. The ultrasound system includes a protective feature that minimizes the introduction of debris into the patient's vasculature if the ultrasound transmission member were to break, fracture or become dislodged during a medical procedure.
2. Description of the Prior Art
A number of ultrasound systems and devices have heretofore been proposed for use in ablating or removing obstructive material from blood vessels. Ultrasound catheters have been utilized to ablate various types of obstructions from blood vessels of humans and animals. Successful applications of ultrasound energy to smaller blood vessels, such as the coronary arteries, requires the use of relatively small diameter ultrasound catheters which are sufficiently small and flexible to undergo transluminal advancement through the tortuous vasculature of the aortic arch and coronary tree. However, because of its small diameter, the ultrasound transmission member which extends through such catheters is particularly susceptible to losses in the transmitted ultrasound energy, and breakage.
Breakage of ultrasound transmission members often occurs near the proximal end thereof, generally at the coupling between the ultrasound catheter coupling and the ultrasound transducer. This is believed to be because energy concentrations and stresses are highest at these points. Thus, any external forces applied to the ultrasound transmission member in this region may result in stresses exceeding the elastic limit of the ultrasound transmission member.
External forces may be inadvertently and undesirably applied to the ultrasound transmission member by pressing upon, pushing, pulling, torquing, bending or bumping the ultrasound transmission member coupling during use of the ultrasound catheter. Such forces when applied to the ultrasound catheter coupling area further result in limited ultrasound energy transmission through the ultrasound transmission member. If ultrasound energy is being transmitted by the ultrasound transmission member at the instant such forces are applied thereto, additional stresses occur which may result in breakage of the ultrasound transmission member.
Breakage of ultrasound transmission members can also occur near the distal end thereof, generally at the area of the smallest cross-section. Therefore, it is important that any debris resulting from the breakage of the ultrasound transmission member not be allowed to be introduced into a patient's vasculature during a medical procedure.
Thus, there still exists a need to protect against breakage of the ultrasound transmission member during a medical procedure.